Hello Sue the Confused!
I am on my second day of a migraine so maybe this will be a case of the blind leading the blind.
Don't get down and dirty with your Brother manual until your migraine has disappeared! Though the Brother manual is an easy read, it would be confusing when you are not feeling well.
The USB ports will handle a USB Flash Drive. A USB Flash Drive can contain the designs you wish to embroider at the moment. Your model may also have other features for the USB Port; I am not familiar with this model. Fonts are already in your machine. Probably not a great number of them. Mine has like (6) different styles. However, if you wish to expand, Brother offers separate Design Cards. You can also download from the ATG site. ATG also offers the Alphabet Xpress, which I own and am extremely impressed by its functions. Brother may have upgrades to your machine in the future. I would imagine that once you register your Model Serial No., Brother would alert you to any and all that may come up. Brother.com would be the official site if you wish to check on that yourself from time to time.
Like anything else new, "baby steps". Learn to thread the machine, then the bobbin, etc. Once you feel comfortable, hit the manual again. Above all else, have fun.
Joan